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Recent land cover change estimates show overall decline of tropical forests at the regional and global scales caused by multiple social, cultural and economic factors. There is an overall concern on the prevailing land use practices, such as shifting cultivation and extraction of forest materials as agents of forests losses, but also new, emerging land uses are threatening tropical forests. Understanding of the long-term development and driving forces of forest changes are needed, especially at local levels where many decisions on forest policies and land uses are made. This paper addresses the importance of such information for improved estimates of forest dynamics by studying local level land cover and land use changes during the last 50–70 years in the Eastern African tropical island of Zanzibar, Tanzania. The paper discusses the role of traditional and new land uses mainly subsistence farming, tourism and government interference through tree planting, in the long-term development of the forests at the village level. The material for the study is gathered from the interpretation of archival maps and aerial photographs combined with contemporary digital aerial photographs. The analyses are based on the mapping, spatial sampling and spatio-temporal change trajectory analysis (LCTA) of forest land cover, forest land uses and settlement patterns with GIS and statistics. Six distinct forest land cover change trajectories were identified and these illustrate dynamic and heterogeneous nature of the forests. Closed forest cover has dominated throughout due to cyclical land use patterns, but over 70% of the land area has been continuously transforming between closed, semi-open and open land cover conditions. Land use turnover rates indicate that hardly any forest areas are left untouched from the forces, which remove and re-establish forest vegetation in the long run. Land cover and land use change trajectories are spatially fragmented in the studied landscape. Majority of forest loss-gain dynamics is caused by shifting cultivation, while forest losses are most dramatic along the coast, where traditional and new land uses meet and land uses pressures are highest. The study suggests that landscape change trajectory analyses, where contemporary and historical information on land uses and land cover changes are spatially linked, can provide valuable aspects into local level forest land use planning and management strategies. For the case study, the findings suggest the following key forest management strategies for consideration: (1) establishment of a protected forest/scrubland in participation with the local stakeholders, especially the farmers, (2) promotion of areas for permanent agricultural practices, while simultaneously introducing management controls in the traditional slash-and-burn farming areas, and (3) promoting new livelihood opportunities for the farmers, who have traditionally been dependent on forest resources, meanwhile introducing alternatives for fuel wood for cooking. 相似文献
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涌(突)水是水利工程引水隧洞施工过程中常见的地质灾害之一,查明掌子面前方富水异常区域的的分布特征是引水隧洞超前预报工作的重要内容.本文结合工程实例介绍了瞬变电磁探测技术在引水隧洞超前预报中的探测和数据处理,表明瞬变电磁法是一种高效的引水隧洞超前预报探测方法,为水利工程引水隧洞施工工作提供有效的技术支撑. 相似文献
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本文采用电感型接近开关,设计了一种用于检测皮带机带速的保护开关,实现了皮带机的欠速保护,并在日照港裕廊股份有限公司皮带机中成功应用。 相似文献
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针对复杂海面背景下红外图像舰船目标由于灰度不均匀、海杂波干扰大等因素造成的自动检测虚警率高、准确率低的问题,提出了一种显著区域提取和目标精确分割相结合的红外舰船目标检测方法。首先,利用基于图论的视觉显著性(Graph-based Visual Saliency ,GBVS)模型计算待检测图像的显著图,使得目标区域信息增强;其次,结合舰船目标先验信息(长短轴、面积等),利用多级阈值划分算法提取关注的显著区域,并确定原图中候选目标区域;最后,利用空间约束模糊C均值(Fuzzy C-Means,FCM)算法对候选区域进行分割,结合目标先验知识对分割区域筛选并输出目标位置。所提方法在公开数据集IRShips上与相关方法进行比较,结果表明,相比直接进行全图目标搜索的方法,所提方法不仅准确率高、执行速度快,且检测目标的位置更加精确。 相似文献
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研制了一个故障集中声光报警系统,以80C196KC单片机为核心,主要包括三部分:信号检测电路、单片机最小系统和故障报警电路。运行结果表明:该系统具有可靠性高、功能强、成本低、维护方便等特点。文中给出了系统框图、硬件电路及软件程序流程图。 相似文献
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传统的观点大都将跳频信号盲检测问题视为能量域的门限阈值问题,而从统计域来看,实际接收到的跳频信号是在一些未知时刻突变而在这些时刻之间保持统计平稳性的分段平稳随机信号,那么基于非平稳时间序列的各种突变检测算法就可以引入其中。分析了当前跳频突变通信信号的统计特性,给出了其高阶分段平稳的模型。将Bemaola-Galan(BG)提出的自适应分割算法推导到高阶,并将其成功应用于多个跳频突发信号盲检测和自适应提取中。仿真结果表明,该算法不需要任何先验信息,能够有效检测和提取多个突发通信信号,且性能优于传统的能量检测法。 相似文献